Final answer:
In meteorological terms, a cold type occlusion may form in an open wave system when the air behind the cold front is the coldest and quickly undercuts the warmer air masses, lifting them aloft.
Step-by-step explanation:
In an open wave system within meteorology, if the air behind the cold front is the coldest of the air masses involved, a cold type occlusion may form. This occurs when the cold front catches up with the warm front and the coldest air mass slides under both the cool and the warmer air masses, pushing the warm air mass aloft completely. This process tends to happen quickly with the initial overtaking, and then the lifting and mixing of the air masses can continue more slowly afterward.